What diltiazem dose is equivalent to 2.5 mg amlodipine?

Dose Equivalence Between Diltiazem and Amlodipine

There is no established pharmacological dose equivalence between diltiazem and amlodipine 2.5 mg, as these are different classes of calcium channel blockers with distinct mechanisms, pharmacokinetics, and clinical effects that cannot be directly converted.

Why Direct Conversion Is Not Possible

Amlodipine (a dihydropyridine) and diltiazem (a non-dihydropyridine) belong to different calcium channel blocker subclasses with fundamentally different properties 1:

• Amlodipine acts primarily on peripheral vascular smooth muscle with minimal cardiac effects 2
• Diltiazem has significant effects on both cardiac conduction (AV node) and vascular smooth muscle 1
• Heart rate effects differ: Diltiazem causes bradycardia while amlodipine typically does not affect heart rate 1, 3

Clinical Context Matters

The choice between these agents should be based on clinical indication rather than dose equivalence 1:

For Hypertension

• Amlodipine starting dose: 2.5-5 mg once daily 1
• Diltiazem ER starting dose: 120-180 mg once daily 1
• Studies show amlodipine produces greater blood pressure reduction than diltiazem at standard doses 3, 4

For Rate Control (SVT/Atrial Fibrillation)

• Diltiazem is preferred due to AV nodal blocking properties 1
• Amlodipine is ineffective for rate control and should not be used 1

For Pulmonary Hypertension (in vasoreactive patients)

• Amlodipine: Start 2.5 mg daily, titrate up to 20 mg daily 1
• Diltiazem: Start 60 mg TID, titrate to 240-720 mg daily 1
• Selection based on baseline heart rate: bradycardia favors amlodipine, tachycardia favors diltiazem 1

Comparative Efficacy Data

Research comparing these agents shows they are not interchangeable 5, 6, 7, 3:

• In hypertension trials, amlodipine 5-10 mg produced significantly greater systolic BP reduction than diltiazem 180-360 mg 3, 4
• In angina studies, amlodipine 5-10 mg once daily was comparable to diltiazem 180 mg/day in divided doses 5, 6, 7
• Amlodipine causes more peripheral edema; diltiazem causes more bradycardia 5, 6, 7

Practical Switching Approach

If switching from amlodipine 2.5 mg to diltiazem 1:

1. Determine the indication: Hypertension, angina, or rate control
2. For hypertension/angina: Start diltiazem ER 120 mg once daily and titrate based on response (not as a direct conversion)
3. For rate control needs: Diltiazem is appropriate; amlodipine is not
4. Monitor closely: Different side effect profiles require reassessment after switching

Critical Contraindications to Consider

Diltiazem should NOT be used if 1:

• AV block greater than first degree without pacemaker
• Decompensated systolic heart failure or severe LV dysfunction
• Sick sinus syndrome without pacemaker
• Concurrent use with beta-blockers (increased bradycardia/heart block risk)

Amlodipine can be used in these situations but avoid in decompensated heart failure 1